The present invention relates to a fuel injector.
From German published application No. 197 57 299, a fuel injector is described in which a fuel injection chamber is arranged downstream of a valve seat. For opening and closing the valve, an axially movable valve needle cooperates with the valve seat, the needle having a conical closing segment corresponding to the contour of the valve seat. Upstream of the valve seat, on the exterior periphery of the valve needle, a diagonally running swirl channel is provided. The swirl channel empties into an annular swirl chamber, which is formed between the valve needle and an external valve housing. From this swirl chamber, the fuel is conveyed to the valve seat. From the fuel injection chamber downstream of the valve seat, the fuel flows into an outlet opening, which begins slightly offset from the center of the base surface of the fuel injection chamber and runs downstream diagonally with respect to the valve longitudinal axis.
The fuel injector according to the present invention has the advantage that it can be manufactured cost-effectively in a particularly simple manner. In this context, the injector, especially at its downstream end, can be assembled in a simple and yet very precise manner. Furthermore, using the fuel injector according to the present invention, very good atomization and very precise spray-discharge of the fuel is achieved, e.g., directly into a cylinder of an internal combustion engine. A particularly uniform front of the spray-discharged spray is attained. In addition, individual streams in the spray of great speed and depth of penetration are avoided.
In a particularly advantageous manner, swirling fuel is fed to the valve seat in the valve seat element over an extremely short flow route. This very short flow route is also guaranteed to the extent that the outlet opening begins immediately at the end of the valve seat surface, avoiding any collector spaces.
The disk-shaped swirl element according to the present invention has a very simple structure and can therefore be shaped in a simple manner. It is the task of the swirl element to generate a swirl or rotary motion in the fuel. Since the swirl element is an individual structural element, its handling in the manufacturing process should not give rise to any limitations.
Ideally, the same disk-shaped swirl element can be used both for a left swirl as well as for a right swirl. By installing the swirl element so that either the front side or the back side is facing the valve seat, this variation can be accomplished extremely simply.
In comparison to swirl bodies that have grooves or similar swirl-producing indentations on an end face, it is possible to create an interior outlet opening area in the swirl element using the simplest of means, the opening area extending over the entire axial thickness of the swirl element and being surrounded by an exterior circumferential edge area.
To guarantee a clear-cut installation position of the swirl element and to avoid mixing up the right swirl and the left swirl, or to design a locking element in the swirl element, installation aids are advantageously pre-molded on the exterior periphery of the swirl element.
By configuring a guide element, which functions to guide the valve needle, as having alternately areas protruding in tooth-like fashion and recesses in between on the exterior periphery, the possibility is created in a simple manner to guarantee an optimal flow into the swirl channels of the swirl element located underneath.
The modular assembly of the guide, swirl, and valve seat elements, as well as the separation of function associated with it, has the advantage that the individual components can be shaped in a very flexible manner, so that through a simple variation of one element, different injecting sprays (spray angle, static injection quantities) can be generated.
The fuel injector according to the present invention in addition to the advantages already mentioned, has the advantage that due to the xe2x80x9cskewedxe2x80x9d arrangement of the outlet opening, swirling, extremely finely atomized fuel sprays can be spray-discharged, in a completely controlled manner, into particularly desirable edge areas, e.g., of a cylinder, without having to abandon, e.g., a desirable hollow cone distribution.
The fuel injector according to the present invention has the advantage that particularly desirable special jet shapes of the spray-discharged fuel can be attained in a simple manner. These are particularly desirable when the internal combustion engine is subject to certain difficult installation conditions or when diagonal but not rotationally symmetrical fuel sprays, e.g., in direct fuel injection, are to be injected into the cylinder of an internal combustion engine, in a completely controlled manner. In this manner, spray cones deviating from an ideal hollow cone are spray-discharged, the cones having a certain shadow area. On the side of the shadow area, the spray cone can act as if it were cut off, as a result of which it is effectively prevented, for example, that the wall is wetted, which is to be avoided on this side.